1. Field of the Invention
The present invention relates to hydraulic cable tensioners, more particularly, to a portable, lightweight hydraulic cable tensioning device for use in tensioning mine roof cable bolts and cable trusses.
2. Prior Art
Hydraulic cable tensioners have been used to apply tension to a length of installed cable having one fixed end such as a conventional cable bolt having a barrel and wedge assembly or a cable truss having a length of cable terminating with a barrel and wedge assembly. Tension is applied to the installed cable between the barrel and wedge assembly and the fixed end of the cable by pulling on the free end of the cable while urging the barrel and wedge assembly towards the fixed end of the cable.
FIG. 1 depicts a conventional cable tensioning unit U formed of three separate steel cylinders, two being hydraulic cylinders HC coupled together via a yoke Y and a central cylinder CC which receives the cable to be tensioned. Hydraulic fluid is fed to the hydraulic cylinders HC via hydraulic lines L and manifolds M from a remote hydraulic fluid supply unit located at a mining machine. The steel unit U is heavy, typically weighing about eighty pounds, and must be held in one place by one operator at the location of the cable bolt or cable truss to be tensioned while a second operator located at the mining machine operates the controls for the hydraulic fluid delivered to the unit U.
The maximum hydraulic pressure applicable to the unit U is about 2,500 psi resulting in tensioning of an installed cable by about eight tons. This conventional cable tensioner is cumbersome due to its weight and need for two people to install and operate the unit.
Accordingly, a need remains for a hydraulic cable tensioning device which may be readily portable and held overhead by one individual as well as operated at the location of the cable bolt or cable truss to be tensioned.